1. Field of the Invention
The present invention relates to a mechanical sensor, and more particularly to a mechanical sensor capable of detecting with high sensitivity, stress or strains.
2. Description of the Related Art
In recent years, under the circumstances that electronic equipment is made smaller and thinner, there is a great demand for further minaturization of mechanical sensors used in electronic equipment. A mechanical sensor utilizing a stress-magnetic effect has been put into practical use (e.g., see SAE Technical Paper Series 920700). Such a mechanical sensor is formed of a cylinder, to which an amorphous magnetic ribbon having a positive magnetostriction constant adheres, and detects the change of the permeability of the amorphous magnetic ribbon due to the stress applied thereto, by using a solenoidal coil.
The above-mentioned conventional mechanical sensor has a coil made of a conductive line with a diameter of about 20 to 30 .mu.m, wound in a solenoidal shape and a magnetic bulk having a thickness of about 20 to 30 .mu.m.
The above-mentioned conventional mechanical sensor has the following problems: Since such a mechanical sensor has a solenoidal coil and a magnetic bulk, it is difficult to miniaturize and integrate the sensor. In addition, since the thickness of the magnetic layer is in the range of 20 to 30 .mu.m, and the diameter of the conductive line is in the range of 20 to 30 .mu.m, there is a limit to the frequency of the sensor.
An example of a planar mechanical sensor suitable for the miniaturization is a strain gauge using a metallic foil. The sensitivity of the strain gauge is one-thousandth or less of that of the mechanical sensor utilizing a stress-magnetic effect.